Webfinger resource to extract username from resource string (#1607)

* Add WebfingerResource class to extract usernames

* Use WebfingerResource in xrd#webfinger

app/controllers/xrd_controller.rb

@@ -31,15 +31,7 @@ class XrdController < ApplicationController
   end
 
   def username_from_resource
-    if resource_param =~ /\Ahttps?:\/\//
-      path_params = Rails.application.routes.recognize_path(resource_param)
-      raise ActiveRecord::RecordNotFound unless path_params[:controller] == 'users' && path_params[:action] == 'show'
-      path_params[:username]
-    else
-      username, domain = resource_param.gsub(/\Aacct:/, '').split('@')
-      raise ActiveRecord::RecordNotFound unless TagManager.instance.local_domain?(domain)
-      username
-    end
+    WebfingerResource.new(resource_param).username
   end
 
   def pem_to_magic_key(public_key)

app/lib/webfinger_resource.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+class WebfingerResource
+  attr_reader :resource
+
+  def initialize(resource)
+    @resource = resource
+  end
+
+  def username
+    case resource
+    when /\Ahttps?/i
+      username_from_url
+    when /\@/
+      username_from_acct
+    else
+      raise(ActiveRecord::RecordNotFound)
+    end
+  end
+
+  private
+
+  def username_from_url
+    if account_show_page?
+      path_params[:username]
+    else
+      raise ActiveRecord::RecordNotFound
+    end
+  end
+
+  def account_show_page?
+    path_params[:controller] == 'accounts' && path_params[:action] == 'show'
+  end
+
+  def path_params
+    Rails.application.routes.recognize_path(resource)
+  end
+
+  def username_from_acct
+    if domain_matches_local?
+      local_username
+    else
+      raise ActiveRecord::RecordNotFound
+    end
+  end
+
+  def split_acct
+    resource_without_acct_string.split('@')
+  end
+
+  def resource_without_acct_string
+    resource.gsub(/\Aacct:/, '')
+  end
+
+  def local_username
+    split_acct.first
+  end
+
+  def local_domain
+    split_acct.last
+  end
+
+  def domain_matches_local?
+    TagManager.instance.local_domain?(local_domain)
+  end
+end

spec/lib/webfinger_resource_spec.rb

@@ -0,0 +1,88 @@
+require 'rails_helper'
+
+describe WebfingerResource do
+  describe '#username' do
+    describe 'with a URL value' do
+      it 'raises with an unrecognized route' do
+        resource = 'https://example.com/users/alice/other'
+
+        expect {
+          WebfingerResource.new(resource).username
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises with a string that doesnt start with URL' do
+        resource = 'website for http://example.com/users/alice/other'
+
+        expect {
+          WebfingerResource.new(resource).username
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'finds the username in a valid https route' do
+        resource = 'https://example.com/users/alice'
+
+        result = WebfingerResource.new(resource).username
+        expect(result).to eq 'alice'
+      end
+
+      it 'finds the username in a mixed case http route' do
+        resource = 'HTTp://exAMPLEe.com/users/alice'
+
+        result = WebfingerResource.new(resource).username
+        expect(result).to eq 'alice'
+      end
+
+      it 'finds the username in a valid http route' do
+        resource = 'http://example.com/users/alice'
+
+        result = WebfingerResource.new(resource).username
+        expect(result).to eq 'alice'
+      end
+    end
+
+    describe 'with a username and hostname value' do
+      it 'raises on a non-local domain' do
+        resource = 'user@remote-host.com'
+
+        expect {
+          WebfingerResource.new(resource).username
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'finds username for a local domain' do
+        Rails.configuration.x.local_domain = 'example.com'
+        resource = 'alice@example.com'
+
+        result = WebfingerResource.new(resource).username
+        expect(result).to eq 'alice'
+      end
+    end
+
+    describe 'with an acct value' do
+      it 'raises on a non-local domain' do
+        resource = 'acct:user@remote-host.com'
+
+        expect {
+          WebfingerResource.new(resource).username
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises on a nonsense domain' do
+        resource = 'acct:user@remote-host@remote-hostess.remote.local@remote'
+
+        expect {
+          WebfingerResource.new(resource).username
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'finds the username for a local account' do
+        Rails.configuration.x.local_domain = 'example.com'
+        resource = 'acct:alice@example.com'
+
+        result = WebfingerResource.new(resource).username
+        expect(result).to eq 'alice'
+      end
+    end
+  end
+end